The present invention relates to magnetic force microscopy.
Heretofore, a soft-magnetic thin film of an iron/nickel alloy or the like as well as a thin film of a platinum/cobalt/chromium alloy or the like has been used to form the tip of a probe of a cantilever magnetic force sensor for detecting a magnetic force by magnetic force microscopy. For instance, some examples of such a cantilever magnetic force sensor have been disclosed in Appl. Phys. Lett., 57, 1820 (1990).
However, such conventional cantilever magnetic force sensors have the following problems. The magnetizing direction of the tip of the probe coated with a soft-magnetic thin film of an iron/nickel alloy or the like fluctuates to be the same as the direction of the lines of the magnetic force of the surface of a sample to be detected with the probe, since the soft-magnetic thin film has a small coercive force Hc. When the surface of a sample is scanned with the probe, the probe always detects only the attractive force irrespective of the direction of the lines of the magnetic force of the surface. Therefore, it was impossible to specifically discriminate the direction of the lines of the magnetic force using the probe. In other words, since the probe of this kind detects only the strength of the magnetic force in order to form an image, it was impossible to determine the recording condition of a vertical magnetic recording medium such as, for example, a photomagnetic disc or the like which records the information to be derived from the reversal of the direction of the magnetic force while the strength of the magnetic force is uniform. On the other hand, the magnetizing direction of the tip of the probe coated with a thin film of a platinum/cobalt/chromium alloy is parallel to the surface of a sample to be detected with the probe. Therefore, when the surface of a sample is scanned with the probe, it is difficult to detect the strength of the lines of the magnetic force in the direction perpendicular to the surface of the sample. For these reasons, it was difficult to determine the recording condition of a vertical magnetic recording medium using the probe. The motion of the probes will be explained with reference to the drawings attached hereto.
FIG. 4 is a graphical view showing the motion of a conventional iron/nickel alloy probe 403 of the prior art. Since an iron/nickel alloy is a soft-magnetic material and has a small coercive force Hc, the magnetizing direction of the probe 403 fluctuates to be the same as the magnetizing direction of the sample to be detected with the probe. Therefore, a constant attractive force is always imparted to the probe 403 irrespective of the magnetizing direction of the sample, and the probe moves in a manner as illustrated in FIG. 4. Hence, measurement of the distribution of the magnetism of the sample is impossible.
FIG. 5 is a graphical view showing the motion of a conventional micro-cantilever magnetic force sensor of the prior art that has a probe 404 coated with a thin film of a platinum/cobalt/chromium alloy. In this case, since the magnetizing direction of the probe 404 is parallel to the surface of the sample to be detected with the probe, it crosses the magnetizing direction of the sample at right angles. Therefore, it is impossible to detect the magnetic force of a sample using such a probe. For these reasons, the probe 404 cannot detect the distribution of the magnetism of the sample, as shown in FIG. 5.
In order to solve the above-mentioned problems, the present invention provides a cantilever magnetic force sensor for magnetic force microscopy, which is composed of a probe coated with a hard-magnetic thin film and a resilently deflectable leaf spring having the probe at its tip.
As mentioned above, since the probe of the invention has a tip coated with a hard-magnetic thin film, the magnetizing direction of the tip of the probe is constant and is perpendicular to the surface of the sample to be detected with the probe, irrespective of the direction of the lines of the magnetic force of the surface of the sample. Therefore, the magnetic force acting on the probe is an attractive force when the direction of the lines of the magnetic force of the surface of the sample is the same as the magnetizing direction of the probe, while it is a repelling force when the direction of the lines of the magnetic force of the surface of the sample is opposite to the direction of the magnetism of the probe. Hence, for example, the probe detects the non-recorded condition of a vertical magnetic recording medium as a repelling force while detecting the recorded condition of the same as the attractive force. Using the probe of the present invention, therefore, it is possible to determine the recording condition of a vertical magnetic recording medium such as, for example, a photomagnetic disc or the like, while such determination has heretofore been difficult using the prior art.